Publishers entering books for the £50,000 Man Booker prize are now being asked to make all submissions available both as physical books and in digital form. This year's judging panel – which includes writers Susan Hill, Matthew d'Ancona, and politician Chris Mullin as well as the Daily Telegraph's head of books Gaby Wood, and is chaired by former M15 chief Stella Rimington – have been issued with e-readers. The move will help them prepare for the 2011 prize longlist, to be announced in July, without hauling around back-breaking numbers of submissions.

Man Booker administrator Ion Trewin said: "Traditionally we rely on proofs and hard copies, but it seemed to me if publishers were in a position to supply us with electronic downloads any earlier, it would help because time is of the essence. And it gives the judges an alternative. This is what the Kindle will do – it's not going to take over from print, but will offer another way of reading as well." The judges who'd responded to him thus far thought the development was "wonderful", Trewin added.

Meanwhile Amazon, posting its latest financial results, said that so far in 2011 its US wing had sold 120 Kindle ebooks for every 100 paperbacks. "Additionally, during this same time period the company has sold three times as many Kindle books as hardcover books," the company said in a statement.

Print still appears to predominate if both editions are taken together, and hard figures are thin on the ground, but the move represents a decisive new shift in the fast-changing balance between traditional and electronic book-buying.

While the numbers of ebook readers in the UK lag well behind their American counterparts, they are growing very swiftly, with huge leaps in sales reported over Christmas. On both sides of the Atlantic, publishers trying to predict the future shape of their business face rapidly moving goalposts. How far the shift to ebooks will go, and how speedily, is still unclear, but at this week's Digital Book World conference in New York, publishers were predicting that 2014 will be the year when ebooks reach parity with print for the first time.